Field of the Invention
The present invention relates generally to the field of devices for controlling the flow of heated gases, smoke, and air to a cooker or oven.
Description of the Prior Art
Kamado style cookers are charcoal burning ceramic devices used for grilling, smoking, roasting, and baking. Kamado style cookers include an air inlet with an air flow control device in the base of the unit to supply air to the charcoal within the cooker and also include an air outlet with an air flow control device in the top of the kamado dome to regulate the rate of air exiting the cooker. The kamado dome is hinged from the kamado bottom, opening upwards to provide access to the interior of the kamado oven. The temperature in the kamado oven is monitored with an analog thermometer set in a hole in the kamado dome or with digital thermometer probes set in the kamado at any desired location. The temperature within the cooker can be controlled by adjusting either one or both vents to regulate the amount of oxygen to the charcoal through natural draft. In typical use, the air flow control device on the kamado's air inlet is open and the kamado's outlet air flow control, usually a daisy wheel, is used to control the temperature in the cooker. A grate is suspended over the charcoal fire within the kamado oven upon which to provide a cooking service for the food.
Kamado style cookers control their internal temperature by regulating the amount of oxygen available to the internal charcoal fire. A thermometer in the kamado provides feedback for temperature control of the cooker. Charcoal is typically used in a kamado instead of wood because of these oxygen-limited conditions. Charcoal is comprised of carbon with some quantities of ash derived from the combustion during charcoal production of other organic materials in the product used to create the charcoal. The type of charcoal used in kamados is typically a hardwood that has been burned at a high temperature (around 1,100 degrees F.) in an environment without oxygen.
A wood fire, combusted under conditions that do not limit the quantity of oxygen to the fire and at an appropriate combustion temperature, can create desirable flavoring gases that are difficult to create or sustain over time with charcoal or in a kamado. Most of the organic materials in the wood that create the desired flavoring gases have been destroyed in the production of the charcoal. However, the charcoal, lacking these organic materials, also does not create the undesirable flavorings that wood creates when combusted under the oxygen-limited conditions or at undesirable temperatures inside a kamado.
A wood fire not limited by oxygen goes through 4 distinct phases of burning indicated by the color of the smoke. The color of wood smoke indicates the sizes of the particles formed by the combustion, which are in turn determined by the temperature of the combustion. From coolest to hottest these are: black smoke (up to 300 degrees F.)-incomplete combustion of the wood resulting in acrid, bitter smoke and creosote; white smoke (300-570 degrees F.)-water evaporating from the wood; blue smoke (desirable) (570-750 degrees)-lightly tinted blue and otherwise clear, sweet smelling, containing desirable gases for flavoring; and no color (clear) (>750 degrees)-too hot to create desirable flavoring gases, though it can be used to cook but without significant smoke flavor.
In the present invention, the kamado is attached or associated with an external firebox assembly which provides heated gases and smoke created and drawn out of the fire chamber in the firebox into the kamado by natural draft or blown by forced draft from the fire chamber by a fan. The firebox assembly allows for the creation and sustaining of a fire that is not oxygen limited and is capable of creating the types of gases and smoke from wood or other combustible material desired for flavoring as well as heat. The amount of heated gases and smoke drawn or blown out of the firebox assembly into the kamado controls the temperature in the kamado, possibly in combination with heat created by a charcoal fire in the kamado and atmospheric air mixed with the heated gases and smoke.
The kamado's air inlet control device is replaced by the air controls in the chimney of the firebox assembly. The chimney's air control devices allow the user to control the rate and proportion of heated gases and smoke with the desired quantity of atmospheric air to be conveyed to the kamado air inlet. The thermometer in the kamado provides feedback to the user of the present invention for temperature control of the cooker.
When using a natural draft to transfer heated gases and smoke from the firebox assembly to the kamado, opening or closing the kamado outlet air flow control on the kamado air outlet controls the rate of heated gas and smoke drawn from the firebox assembly to the kamado and regulates the temperature in the kamado. Excess heated gases and smoke goes out the firebox assembly door. When using a forced draft to transfer the heated gases and smoke to the kamado, the temperature of the kamado is regulated by either air flow rate as controlled by a fan or the feed rate of combustion material, or both. In both cases, the combustion material is not limited in its combustion by the availability of oxygen.
In the above, it can be seen that it is advantageous to create a combustion source not limited by oxygen and capable of achieving a combustion temperature adequate to create desirable flavoring gases, and control the flow of this heated gas and smoke to the kamado. The firebox assembly disclosed herein includes valves or gates that allow control of each component, namely, heated gas, smoke, and outside air to the kamado thereby allowing the user to obtain optimum results by controlling the valves associated with the firebox assembly and the kamado's top outlet air flow control device.